This lays out the reasons to stay fit in terms that cannot be denied!

Increasing BMI was associated with increased risk of the following cancers: endometrial cancer (trend in relative risk per 10 units = 2.89), adenocarcinoma of the esophagus (2.38), kidney cancer (1.53), leukemia (1.50), multiple myeloma (1.31), pancreatic cancer (1.24), non-Hodgkin's lymphoma (1.17), ovarian cancer (1.14), breast cancer in post-menopausal women (1.40), colorectal cancer in pre-menopausal women (1.61), and all cancers combined (1.12). Similar associations were found between BMI and risk of mortality from cancer. The authors state, "Among postmenopausal women in the UK, 5% of all cancers (about 6000 annually) are attributable to being overweight or obese. For endometrial cancer and adenocarcinoma of the oesophagus, body mass index represents a major modifiable risk factor; about half of all cases in postmenopausal women are attributable to overweight or obesity."

Increasing Body Mass Index Linked to Increased Incidence of Cancer